On Joint Impact of HPA Non-Linearity and Imperfect SIC in NOMA Enabled HCN Using Stochastic Geometry

A multi-tier architecture consisting of a macro-base station (MBS) and a pico-base station (PBS) is utilized in a heterogeneous cellular network (HCN) to support a large number of users requiring higher data rates with enhanced performance. For the upcoming sixth-generation wireless networks, the spectrally efficient non-orthogonal multiple access (NOMA) technique is utilized to serve a large number of users. To increase power efficiency and improve outage probability, the power amplifier at the base station is operated close to saturation, which causes non-linear distortions (NLD). Thus, it is essential to understand the underlying performance guarantees of NOMA-enabled HCN systems (HCN-NOMA) under the non-linear distortions by the high power amplifiers (HPA). This study applies the stochastic geometric approach to analyze the performance of HCN-NOMA under imperfect successive interference cancellation (ipSIC) in HCN with NLD. Orthogonal multiple access (OMA) and NOMA under both perfect and ipSIC in multi-tier HCN are compared. The performance is assessed and compared in terms of outage probability, ergodic capacity, system throughput, and energy efficiency. It is observed that the performance is improved by up to 96% by employing NOMA as compared to OMA while operating in the non-linear region of the HPA. Even with the ipSIC, significant performance gains of up to 93% are observed as compared with OMA in the non-linear region of operation.